For hydrogen generation, steam and a hydrocarbon compound (CxHy, organic compound, hydrocarbon mixture) are made to react at high temperature in a catalytic converter.
European Patent Disclosure EP 0 848 989 A2 discloses a co-current or countercurrent reactor which includes a monolithic element with many conduits parallel to one another, which are divided into two groups interested with one another. The reactants (educts) flow through one group, while a mixture of combustion gas and air flows through the other. If steam is among the reactants, then it must be generated separately.
U.S. Pat. No. 5,484,577 discloses a reformer with a combustion chamber that is heated via a gas burner. A substantially cylindrical reaction vessel is disposed in the combustion chamber, and its outer jacket is heated by the gas flame produced and by the hot combustion gases. Catalyst pellets are disposed in an outer ring region in the reaction vessel. The reaction gas mixture flows through the catalyst pellets and through a cylindrical return conduit to the gas outlet. The reactants are delivered in the form of gas or steam.
U.S. Pat. No. 5,811,065 also discloses a similar reformer which combines a plurality of reformers into a reformer battery.
In recent times, small reformer systems with a capacity of about 1 to 200 Nm3/h of hydrogen are needed for producing hydrogen as process gas or protective gas and to generate current using fuel cells. In such compact reformers, attempts to optimize the thermal economy are made in various ways.
The use of reformers to produce hydrogen for fuel cells, especially in small power plants with a capacity in the range from 5 kW to 20 kW, necessitates fast adaptation of the water production to load changes. The hydrogen yield should be equivalent to that of large systems. If natural gas is used as the starting gas, this means approximately 2.5 to 2.7 m3 of hydrogen, per m2 of natural gas. This is equivalent to an efficiency for energy conversion of 75 to 80%, in each case referred to the lower calorific value.
A need therefore remains for a reformer for producing hydrogen from hydrocarbons by steam reformation which is capable of handling rapid load changes within a short period of time and is capable of generating steam for the reformation process.
The invention provides such a reformer and a method for producing hydrogen from water and hydrocarbons via steam reformation. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.